Change this sentence into negative form virtual libraries often contain more up-to-date information ​

it is already in negative form?

Explanation:

it would be d). more resources must be obtained to attain that combination of goods and services

hygrometers and hair thermometers (often found as part of hygrometers/psychrometers) can be used to measure humidity. barometers are used to measure atmospheric pressure, while anemometers are used to measure wind speed. so the 2nd and 4th choices should be the correct answers.